   #copyright

Common cold

2007 Schools Wikipedia Selection. Related subjects: Health and medicine

   CAPTION: Acute nasopharyngitis
   Classifications and external resources

     ICD- 10   J 00.0
     ICD- 9    460
   DiseasesDB  31088
   MedlinePlus 000678
    eMedicine  med/2339
   MeSH        C08.730.162

   Acute viral nasopharyngitis, often known as the common cold, is a mild
   viral infectious disease of the upper respiratory system ( nose and
   throat). Symptoms include sneezing, sniffling, runny nose, nasal
   congestion; scratchy, sore, or phlegmy throat; coughing; headache; and
   tiredness. Colds typically last three to five days, with residual
   coughing lasting up to three weeks. It is the most common of all human
   diseases, infecting adults at an average rate of 2-4 infections per
   year, and school aged children as many as 12 times per year. Infection
   rates greater than three infections per year per person are not
   uncommon in some populations. Children and their parents or caretakers
   are at a higher risk, possibly due to the high population density of
   schools and the fact that transmission to family members is highly
   efficient.

   The common cold belongs to the upper respiratory tract infections. It
   is different from influenza, a more severe viral infection of the
   respiratory tract that shows the additional symptoms of rapidly rising
   fever, chills, and body and muscle aches. While the common cold itself
   is rarely life threatening, its complications, such as pneumonia, can
   very well be.

Pathology

   The common cold is caused by numerous viruses (mainly rhinoviruses,
   coronaviruses, and also certain echoviruses, paramyxoviruses, and
   coxsackieviruses) infecting the upper respiratory system. Several
   hundred cold-causing viruses have been described, and a virus can
   evolve to survive, ensuring that any cure is still a long way off. The
   nasopharynx is the central area infected. The reasons that the virus
   concentrates in the nasopharynx rather than the throat may be the low
   temperature and high concentration of cells with receptors needed by
   the virus.

Transmission

   The viruses are transmitted from person to person by droplets from
   coughs or sneezes. The droplets or droplet nuclei are either inhaled
   directly, or transmitted from hand to hand via handshakes or objects
   such as door knobs, and then introduced to the nasal passages when the
   hand touches the nose or eyes.

   The virus takes advantage of sneezes and coughs to infect the next
   person before it is defeated by the body's immune system. Sneezes expel
   a significantly larger concentration of virus "cloud" than coughing.
   The "cloud" is partly invisible and falls at a rate slow enough to last
   for hours—with part of the droplet nuclei evaporating and leaving much
   smaller and invisible "droplet nuclei" in the air. Droplets from
   turbulent sneezing or coughing or hand contact also can last for hours
   on surfaces, although less virus can be recovered from porous surfaces
   such as wood or paper towel than non-porous surfaces such as a metal
   bar. A sufferer is most infectious within the first three days of the
   illness. Symptoms, however, are not necessary for viral shedding or
   transmission, as a percentage of asymptomatic subjects exhibit viruses
   in nasal swabs, likely controlling the virus at concentrations too low
   for them to have symptoms.

Mechanism of Infection

   The virus enters the cells of the lining of the nasopharynx (the area
   between the nose and throat), and rapidly multiplies. The major entry
   point is normally the nose, but can also be the eyes (in this case
   drainage into the nasopharynx would occur through the Nasolacrimal
   duct). The mouth is not a major point of entry and transmission does
   not usually occur with kissing or swallowing.

   The virus enters the cell by binding to ICAM-1 receptors in these
   cells. The presence of ICAM-1 affects whether a cell will be infected.
   Its concentration also can be affected by various other factors,
   including allergic rhinitis and some other irritants including
   rhinoviruses themselves. ICAM-1 has been a major focal point in drug
   research into cold treatments.

Symptoms

   Ninety-five percent of people exposed to a cold virus become infected,
   although only 75% show symptoms. The symptoms start 1–2 days after
   infection. Generally a cold starts with a sore throat, without any
   respiratory blockage. From then onwards the symptoms are a result of
   the body's defense mechanisms: sneezes, runny nose, and coughs to expel
   the invader, and inflammation to attract and activate immune cells.

   After a common cold, a sufferer develops immunity to the particular
   virus encountered. However, because of the large number of different
   cold viruses, this immunity offers limited protection. A person
   therefore can be easily infected by a different type of cold virus,
   starting the process all over again.

Complications

   Bacteria that are normally present in the respiratory tract can take
   advantage of the weakened immune system during a common cold and
   produce a coinfection. Middle ear infection (in children) and bacterial
   sinusitis are common coinfections. A possible explanation for these
   coinfections is that strong blowing of the nose drives nasal fluids
   into those areas.

   The best way to blow the nose is keeping both nasal openings open when
   blowing and wiping rather than fully covering them, permitting pressure
   to partially dissipate. Doing so will reduce the pressure that would
   otherwise drive fluid into the ears or sinuses.

Prevention

   The best way to avoid a cold is to avoid close contact with existing
   sufferers, to wash hands thoroughly and regularly, and to avoid
   touching the face. Anti-bacterial soaps have no effect on the cold
   virus—it is the mechanical action of hand washing that removes the
   virus particles. In 2002, the Centers for Disease Control and
   Prevention recommended alcohol based hand gels as an effective method
   for reducing infectious viruses on the hands. However, as with standard
   handwashing, alcohol gels provide no residual protection from
   re-infection. Tobacco smoking has also been linked with the weakening
   of the immune system; non-smokers are known on average to take fewer
   days off sick than the smoking population.

   Because of the large variety of viruses causing the common cold,
   vaccination is impractical.

Treatment

   There is no cure for the common cold—no medically-proven treatment that
   directly fights the virus.

   Only the body's immune system can effectively destroy the invader, a
   process which generally takes about 7 days in healthy individuals. Warm
   clothing, including socks are found by most to alleviate the suffering.
   A cold may be composed of several million viral particles, and
   typically within a few days, the body begins mass producing a better
   tailored antibody that can prevent the virus from infecting cells, as
   well as white blood cells which destroy the virus through phagocytosis
   and destroy infected cells to prevent further viral replication. Since
   the duration of infection is on the order of a few days to one week,
   even a proven cure could only reduce the duration by a few days. That
   said, there are both experimental pharmaceutical and unproven natural
   remedies.

Antibiotics

   Antibiotics are not a cold remedy. Antibiotics do not treat viral
   infections, and thus are ineffective against the common cold. Treatment
   of colds with antibiotics can be counterproductive, as it can promote
   the production of drug resistant bacteria, and can even promote
   infections by killing off normal bodily flora. However, antibiotics may
   be useful for treating coinfections such as a middle ear infection.

Echinacea

   Although there have been scientific studies done on echinacea, its
   effectiveness has not been demonstrated. A peer-reviewed clinical study
   published in the New England Journal of Medicine concluded that
   ...extracts of E. angustifolia root, either alone or in combination, do
   not have clinically significant effects on rhinovirus infection or on
   the clinical illness that results from it. Even if you are using
   echinacea, it's not advised to use it more than two weeks continuously.
   .

Anti-virals

   ViroPharma Incorporated and Schering-Plough have been developing an
   anti-viral drug that targets picornaviruses, the viruses that cause the
   majority of common colds. Pleconaril has been shown to be effective in
   an oral form, but significant side effects make current formulations
   unsafe. Schering-Plough is developing an intra-nasal formulation that
   may overcome some of these safety issues. However, it may not be until
   2008 or 2009 that the drug is on the market.

   Let's play!

Interferons

   Interferons, natural proteins produced by the cells of the immune
   system, can be administered intranasally in low doses. In Eastern
   Europe, Russia, and Japan this is used as a method to prevent and treat
   viral respiratory diseases such as cold and flu, though most western
   doctors dispute the effectiveness of this treatment. Work is currently
   being done on interferon lozenges as an alternative method of delivery.

Vitamin C

   Publications in the 1960s and 1970s suggested that large doses of
   vitamin C could both prevent and reduce the effects of the common cold.
   A well known supporter of this theory was Nobel Prize winner Linus
   Pauling, who publicly advocated the intake of large doses of vitamin C
   to prevent infection. In 1970 he wrote the bestseller Vitamin C and the
   Common Cold. A meta-analysis published in 2005 found that vitamin C
   reduced the incidence of colds by 50% in six trials with physically
   stressed participants, but that 200^+mg daily had no effect on the
   incidence of colds in ordinary people. Regular vitamin C
   supplementation shortened the duration of colds in children by 14% and
   in adults by 8%.

   Findings from therapeutic trials of dosages under 6 grams per day and
   single doses^ have been conflicting. It is worth noting that none of
   the recent conventional therapeutic trials carried out so far have
   examined the effect of vitamin C on children, although the regular
   supplementation trials have shown a substantially greater effect on
   episode duration in children. A 2006 dissertation extensively reviews
   the conventional medical trial data, analyses, problems and history on
   vitamin C at length. The dissertation dissects many previous
   conventional analyses for errors that influence public policy and major
   textbooks. It suggests that therapeutic vitamin C levels to alleviate
   respiratory illness and that certain subgroups who might benefit from
   supplementation warrant more research. The 2006 dissertation also
   suggests that maintaining a double blind trial for dosages of 6 grams
   per day or more of vitamin C may be fundamentally difficult as test
   participants begin to perceive differences with placebos.

   The Vitamin C Foundation recommends an initial usage of up to 8 grams
   of vitamin C every 20-30 minutes in order to show an effect on the
   symptoms of a cold infection that is in progress. Most of the studies
   showing little or no effect employ doses of ascorbate such as 100 mg to
   500 mg per day, considered "small" by vitamin C advocates. Equally
   important, the plasma half life of high dose ascorbate above the
   baseline, controlled by renal resorption, is approximately 30 minutes,
   which implies that most high dose studies have been methodologically
   defective and would be expected to show a minimum benefit. Clinical
   studies of divided dose supplementation, predicted on pharmacological
   grounds to be effective, have only rarely been reported in the
   literature.

   Because vitamin C is metabolized to oxalic acid in the body, some
   scientists have long speculated that high doses may contribute to the
   development of kidney stones. Such hypotheses have so far proven
   inconclusive with other aggravating and mitigating factors being better
   identified.

   The United States Department of Agriculture recommends a minimum daily
   requirement of 75mg to 90mg Vitamin C for adults and 120mg for
   lactating females, while the European Commission Health and Consumer
   Protection DG recommends a minimum of 60mg for all adults.

Zinc preparations

   Zinc-containing lozenges were first claimed to be effective in the
   treatment of cold infections by Eby, Davis and Halcomb. There have been
   a number of clinical studies of the efficacy of zinc, some of which
   have shown an effect and some of which have shown no effect.

   A 1997 meta-analysis of six clinical studies concluded that Despite
   numerous randomized trials, the evidence for effectiveness of zinc
   salts lozenges in reducing the duration of common colds is still
   lacking. A 1999 scientific review of published data concluded: Overall,
   the results suggest that treatment with zinc lozenges did not reduce
   the duration of cold symptoms. Evidence of the effects of zinc lozenges
   for treating the common cold is inconclusive. Given the potential for
   treatment to produce side effects, the use of zinc lozenges to treat
   cold symptoms deserves further study. Another scientific review by
   George Eby in 2004, one that considered the solution chemistry of all
   zinc lozenge formulations tested from 1984 through 2004, showed a
   statistically significant dose response when the amount of ionic zinc,
   rather than total zinc, was considered. However, Eby and Halcomb failed
   to show any efficacy from zinc gluconate nasal sprays in 2006, and
   suggested why some throat lozenges are effective, while nasal
   application is not effective.

   There are concerns regarding the safety of long-term use of cold
   preparations in an estimated 25 million persons who are
   haemochromatosis heterozygotes. Another concern with use of very
   high-dose zinc for more than two weeks is copper depletion, which leads
   to anaemia.

   Although widely available and advertised in the United States, the
   safety and efficacy of zinc preparations have not been evaluated or
   approved by the Food and Drug Administration, and they are not likely
   to have any utility against colds due to removal of ionic zinc through
   additive food acids ( citric acid, ascorbic acid and glycine).
   Consequently, a "cure for the common cold" using zinc acetate lozenges
   without additive food acids is not available due to marketing, rather
   than scientific, considerations. In the United Kingdom, the National
   Health Service includes zinc lozenges in a list of not-recommended
   treatments.

   Zicam Cold Remedy is a non-drip nasal gel containing Zincum Gluconicum
   to "Reduce the duration; Reduce the severity of the common cold." A
   2000 study on the nasal gel has indicated that if taken within 24 hours
   of the initial cold symptoms it can shorten a cold significantly.
   Comparing the 50% symptom threshold (where the percent of patients
   reporting symptoms had dropped from 100% to 50%), the zinc group
   attained the 50% threshold in 2 days while the placebo group attained
   it in 9 days. The nasal gel works best when taken within 24 hours of
   the first symptoms of a cold. A 2002 study recruited patients who had
   experienced cold symptoms for 24-48 hours (therefore outside the
   recommended window of opportunity) and found that the median time to
   cold resolution was still significantly shorter in the zinc vs. the
   placebo group, with the zinc group’s colds approximately 2 days shorter
   that the placebo group’s colds. A lawsuit against the company that
   makes Zicam Cold Remedy filed by people who claimed that the nasal gel
   caused them to lose their sense of smell was settled out of court for
   $12,000,000 but the company did not admit fault.

Non-Cure Treatments

   Though cures are unproven, there are a number of effective treatments
   which, rather than treat the viral infection, focus on relieving the
   symptoms. For some people, colds are relatively minor inconveniences
   and they can go on with their daily activities with tolerable
   discomfort. This discomfort has to be weighed against the price and
   possible side effects of the remedies, and the possibility, though not
   scientifically proven, that by suppressing responses evolved to fight
   the cold, the symptom suppressants may prolong the illness.

   Common treatments include: analgesics such as aspirin or paracetamol
   (acetaminophen), as well as localised versions targeting the throat
   (often delivered in lozenge form), nasal decongestants such as
   phenylephrine HCI which reduce the inflammation in the nasal passages
   by constricting local blood vessels, cough suppressants (which work to
   suppress the cough reflex of the brain or by diluting the mucus in the
   lungs), and first-generation anti-histamines such as brompheniramine,
   chlorpheniramine, and clemastine (which reduce mucus gland secretion
   and thus combat blocked/runny noses but also may make the user drowsy).
   Second generation anti-histamines do not have a useful effect on colds.

   A warm and humid environment and drinking lots of fluids, especially
   hot liquids, can alleviate symptoms somewhat. Common home remedies
   include chamomile, lemon or ginger root tisanes and soup (which
   probably work by soothing the irritated respiratory passages with their
   steam), nebulized medicinal mixtures, hot compresses, mustard plasters,
   hot toddies, tamagozake, licorice and echinacea. Eating spicy food can
   help alleviate congestion, although it may also irritate the
   already-tender throat. Coffee, or its active component, caffeine, has
   also been shown to improve mood and mental performance during
   rhinovirus infection.

   Other home remedies include gargling and flushing the nose with salt
   water. A strong salt solution reduces swelling in the throat and nasal
   tissue through osmosis. The high saline concentration draws fluids out
   of the cells through the cell membranes. This helps reduce the
   irritations in the throat and can clear the nasal passages and restore
   easy breathing without the use of medication. It is better to use
   iodine free salt. Iodine has a bitter taste and may irritate the nasal
   tissues. A common technique for flushing the sinus is to use a Jala
   neti pot. However a flexible cup or commercial sinus squirt bottle also
   works very well.

Societal impact

   Common colds interfere with school attendance and can cause lost days
   on the job, resulting in considerable costs to the economy. In
   addition, a lot of money is spent on over-the-counter and home
   remedies.

   Arguably the most common communicable disorder that humans can be
   afflicted with, the cold is considered something of a common cultural
   point of reference. Thus, catching a cold is often used as a plot
   device in various stories, movies, and television series.

   Many companies offer a number of paid sick days per year to avoid
   errors during work and transmission to co-workers. In many countries
   this is mandated by law.

   University of Michigan researcher Dr. A. Mark Fendrick published 2003
   study on effects of the common cold in the United States. The study
   found that the common cold leads to more than 100 million physician
   visits annually at a conservative cost estimate of $7.7 billion per
   year. More than one-third of patients who saw a doctor received an
   antibiotic prescription, which Fendrick says not only contributes to
   unnecessary costs, but also has implications for antibiotic resistance
   from overuse of such drugs.

   The study found that Americans spend $2.9 billion on over-the-counter
   drugs and another $400 million on prescription medicines for
   symptomatic relief. Additionally, cold sufferers spend $1.1 billion
   annually on an estimated 41 million antibiotic prescriptions, even
   though the drugs have no effect on a viral illness.

   The study reports that an estimated 189 million school days are missed
   annually due to a cold. As a result, parents missed 126 million
   workdays to stay home to care for their children. When added to the
   workdays missed by employees suffering from a cold, the total economic
   impact of cold-related work loss exceeds $20 billion. In the UK,
   £67,692,708.08 were lost in the cause of workdays lost due to
   rhinovirus.

History

   Colds were known in ancient Egypt; there were hieroglyphs representing
   the cough and the common cold. The Greek physician Hippocrates gave a
   description of the disease in the 5th century BC. The common cold was
   also known among the ancient American Indian Aztec and Maya
   civilizations. A mixture of chili pepper, honey, and tobacco was one
   common Aztec treatment for colds.

   In the 18th century, John Wesley wrote a book about curing diseases; it
   advised against cold baths, stating that chilling causes the common
   cold. The work was widely reprinted in the 19th century. Another book
   by William Buchan in the 18th century also gave wet feet and clothes as
   the cause of the common cold.

   The idea that microscopic infectious agents cause disease arose in the
   second half of the 19th century. Initially, bacteria were suspected to
   be the cause of the common cold, and vaccines were produced based on
   this theory; these were still prescribed in the 1950s.

   Viruses had been described beginning in the 1890s: infectious agents so
   small that they could pass through all filters and could not be seen
   under a microscope. In 1914, Walter Kruse, a professor in Leipzig,
   Germany, showed that viruses caused the common cold: nose secretions of
   a cold sufferer were diluted, filtered, and introduced into the noses
   of volunteers, producing colds in about half of the cases. These
   findings were not widely accepted, until they were repeated in the
   1920s by Alphonse Dochez, first in chimpanzees, and then in human
   volunteers using a double-blind setup. Nevertheless, in 1932 a major
   textbook on the common cold by David Thomson still presented bacteria
   as the most likely cause.

   In the United Kingdom, the Common Cold Unit was set up by the civilian
   Medical Research Council in 1946. The unit worked with volunteers who
   were infected with various viruses. The rhinovirus was discovered
   there. In the late 1950s, researchers were able to grow one of these
   cold viruses in a tissue culture, as it would not grow in fertilized
   chicken eggs, the method used for many other viruses. In the 1970s, the
   CCU demonstrated that treatment with interferon during the incubation
   phase of rhinovirus infection protects somewhat against the disease,
   but no practical treatment could be developed. The unit was closed in
   1989, just two years after it demonstrated the benefit of zinc
   gluconate lozenges in the prophylaxis and treatment of rhinovirus
   colds.

"Cold" as misnomer

   Originally, the term "cold" may have referred to a "cold condition"
   such as the hot, cold, dry, and wet "conditions" described by the
   ancient Anatolian physician Galen, but the climate is only an enabler
   and not the cause. Colds are somewhat more common in winter, and cold
   climate may affect transmission by causing people to stay indoors where
   ventilation is reduced and proximity to infected persons is increased,
   but the cause of the infection remains viral. Some allergies, bacterial
   respiratory infections, and even climate changes can also cause
   common-cold-like symptoms that can last for days.

   Infection with a cold virus affects thermogenesis. This makes people
   associate post-infection shivering with situations in which they were
   exposed to cold that intensifies shivering (e.g. wet hair, draft, long
   wait on a bus stop, etc.). This association helps propagate the myth.

   If cold weather were directly linked to the spread of the common cold,
   then it could possibly be demonstrated by comparing the infection rates
   of people who live in colder climates (such as Iceland or Greenland)
   with people who live in warmer climates (such as countries close to the
   equator). Studies done in the 1960s found no significant increase in
   infection rates in people who live in colder climates.

   It is not known conclusively whether cold weather or a humid climate
   can affect transmission by other means, such as by affecting the immune
   system, or ICAM-1 receptor concentration, or simply increasing the
   amount and frequency of nasal secretions and frequency of hand to face
   contact. A person can best avoid colds by avoiding those who are ill
   and the objects that they touch, as well as by keeping their immune
   system in top form by getting enough sleep, reducing stress, eating
   nutritious foods, and avoiding excess alcohol consumption.

   In a widely-publicized and yet seriously flawed experiment, researchers
   at the Common Cold Centre at the Cardiff University attempted to
   demonstrate that cold temperatures can lead to a greater susceptibility
   to viral infection. They showed that a small group of people who sat
   with their feet in cold water for 20 minutes a day for a week had a 1
   in 3 chance of developing cold symptoms during that week, while a
   control group who were not exposed to the chill had a 1 in 10 chance
   (this probability corresponds with the implausible 1 in 239 chance of
   surviving a year without catching a cold). According to Dr. Ronald
   Turner the study is seriously flawed because the researchers used
   symptom questionnaires instead of actual infection detection and failed
   to check whether the participants were already infected or not.
   Multiple other studies have failed to find a link between low
   temperatures and infection.

   Many languages reflect the unfounded belief that exposure to cold
   increases the risk of catching a cold virus

   Retrieved from " http://en.wikipedia.org/wiki/Common_cold"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
